Energy saving and pollution reduction considerations, particularly in urban surroundings, have led automotive vehicle manufacturers to equip their models with an automatic heat engine stop/restart system such as the system known as the “Stop and Go” system.
As discussed in VALEO EQUIPEMENTS ELECTRIQUES MOTEUR's French patent document FR 2 875 549, vehicles are rendered capable of functioning in “Stop and Go” mode by dint of a reversible electric machine, or starter-alternator, coupled to a heat engine supplied by an AC/DC converter in “starter” mode.
Under certain conditions, using a starter-alternator in the “Stop and Go” functional mode consists of causing the heat engine to stop completely when the vehicle itself is stopped, then restarting the heat engine subsequent, for example, to an action of the driver which is interpreted as a restart command.
A typical “Stop and Go” situation is that of stopping at a red light. When the vehicle stops at the light, the heat engine is automatically stopped, then when the light turns green, the engine is restarted using the starter-alternator following detection by the system of the clutch pedal being depressed by the driver or of any other action which is interpreted as meaning that the driver intends to restart the vehicle.
Essentially, such an automatic heat engine stop/restart system is currently provided on particular cars, but clearly there is an interest in generalizing its use to other types of vehicles for the purposes of saving energy and preserving the environment in a town driving situation.
A major source of pollution is constituted by utility vehicle engines, especially those of lorries, buses and other service or public transport vehicles.
Thus, it is natural to envisage installing a “Stop and Go” type system in such categories of vehicles in order to reduce their average fuel consumption and their polluting emissions.
The heat engines which equip such vehicles are large cubic capacity diesel or petrol engines, which demand the use of starter-alternators with specific torque and power characteristics which differ from those of the starter-alternators mounted on private small cubic capacity vehicles.
However, for obvious cost reduction reasons, designing a starter-alternator dedicated solely to starting large engines is to be avoided.